How to monitor users
I want to monitor user per user not per IP
and want to know what are they doing on their devices ?
No need for fancy tools for that. Let me save you some time, I can tell you what they're doing… Facebook, Instagram, Snapchat, YouTube, Netflix, YouPorn........................... ;)
Just block everything and then whitelist what you want to allow them to access and call it a day. Trying to monitor is (mostly) a lost cause now that everything is HTTPS.
Some starting points, check out pfBlockerNG, and https://doc.pfsense.org/index.php/Blocking_websites
I use Squid as a transparent proxy and LightSquid for reporting web traffic. For other forms of traffic you can use ntopng though it's not intuitive. And both of these solutions are not per-user but rather per-device. If you need per-user monitoring you'll need to look at something installed on the client workstation.